The invention relates to a junction field effect transistor (JFET) affording high blocking voltage capability, including AC application.
A power JFET is provided with a stack of alternating conductivity type layers forming a plurality of channels. Bidirectional current is conducted through the channels in an ON state. In the OFF state, current flow is blocked by depletion region pinch-off in the channels.
In preferred form, ON state conduction current flows longitudinally horizontally through the channels and through a drift region of like conductivity type as the channels, with consequent desirable bulk effect characteristics. The channels are stacked vertically at the end of the drift region, with current flowing horizontally through the channels in the ON state, and being pinched-off in the OFF state by vertical depletion region spreading. A drift region may be provided at one or both ends of the stacked channels. Linear geometry enables desirable control of breakdown voltage, and in turn a higher blocking voltage capability. Multiple channels reduce the channel component of the ON state resistance.
Further in the preferred form, field shaping regions are provided in the drift region for straightening field lines therein and reducing gradient curvature crowding of the field lines, e.g., radius or corner curvature. The field shaping regions are in the bulk drift region, removed from the active area of the channel junctions between the alternate conductivity layers in the stack.